I just noticed I had the gas tank cracks on a 2009 F800GS I bought a couple months ago.

Brought the bike to my local dealer for 6K scheduled maintenance and he informed me that he should be able to replace the tank under warranty - even though the bike is past its 3 year original warranty. Apparently there is an additional warranty period of 5 years for fuel and EFI related stuff.

Free new tank hopefully!!

But he also said the same thing will happen since its the exact same part number.

I had not thought about extended warranty on fuel system components..............
My tank started cracking after about a year, I waited till just inside the 3-year warranty period to have it replaced,
having been told that BMW-parts warranty was 2-years from date of purchase. The new one has cracked also,
so far not very badly ... hopefully it will be cracked badly enough to not get into a fight about having it replaced next fall........ pity they can't get this right .......

I had not thought about extended warranty on fuel system components..............
My tank started cracking after about a year, I waited till just inside the 3-year warranty period to have it replaced,
having been told that BMW-parts warranty was 2-years from date of purchase. The new one has cracked also,
so far not very badly ... hopefully it will be cracked badly enough to not get into a fight about having it replaced next fall........ pity they can't get this right .......

The shop I go to is very honest and they seem to know their sh*t. He was telling me it is an ethanol issue where it is absorbed by the tank plastic causing expansion, swelling and eventually the cracking. It is affecting primarily US and Canadian bikes. Ducati is also badly affected he tells me - worse than BMW. He is on his third tank.

The good news is that it is purely a cosmetic issue and apparently no one has had a failure leading to leaking gasoline. Most likely if that were to start happening BMW would be recalling the tanks. How the swelling and cracking only affects the outer cosmetic wall of the tank I have no idea.

The bad news is that BMW won't likely be changing the tank and any replacement tank is the same part number, same problem. The switch will "buy you a couple years" I'm told.

Oh well! I'll take a new tank soon hopefully and live with some cracks when they recur.

This "ethanol" related cause seems rather illogical....since the outer shell does not contact the fuel.

I think it's a stress fracture along a weak point, caused by imposed forces ( weight of fuel + vibration + bouncing, shaking, etc ) and maybe some premature aging ( hardening...brittleness). But what do I know?

My cracked tank was replaced under warranty this past summer by Gateway BMW, St. Louis. No fuss....they were very accommodating and expedient.

This "ethanol" related cause seems rather illogical....since the outer shell does not contact the fuel.

I think it's a stress fracture along a weak point, caused by imposed forces ( weight of fuel + vibration + bouncing, shaking, etc ) and maybe some premature aging ( hardening...brittleness). But what do I know?

My cracked tank was replaced under warranty this past summer by Gateway BMW, St. Louis. No fuss....they were very accommodating and expedient.

HF

Actually i agree with you. But the stress along the weak point on the tank and the resulting cracks are ultimately coming from the tank becoming slightly deformed from the ethanol. It's a known issue to both BMW and Ducati, and it is only affecting bikes where ethanol is commonly added. Other countries are not having this problem, i.e. it's not the weight, shaking, bouncing etc.

For a while I thought it might be the canister system ... but I then found out that even the Eurozone bikes still have the 2-way check valve in the vent line that is used to control the flow of vapors in the canister system...

If the inner liner (exposed to ethanol) swells it would then put tensile stress on the outer plastic "shell",
and that "ridge line" where everyone's tank tends to crack is a natural stress-raiser....

I'm open to other possibilities, but haven't really heard any that make sense...........

The shop I go to is very honest and they seem to know their sh*t. He was telling me it is an ethanol issue where it is absorbed by the tank plastic causing expansion, swelling and eventually the cracking. It is affecting primarily US and Canadian bikes. Ducati is also badly affected he tells me - worse than BMW. He is on his third tank.

The good news is that it is purely a cosmetic issue and apparently no one has had a failure leading to leaking gasoline. Most likely if that were to start happening BMW would be recalling the tanks. How the swelling and cracking only affects the outer cosmetic wall of the tank I have no idea.

The bad news is that BMW won't likely be changing the tank and any replacement tank is the same part number, same problem. The switch will "buy you a couple years" I'm told.

Oh well! I'll take a new tank soon hopefully and live with some cracks when they recur.

Well... In that case they don't know $h!^..... as there are no contact between the liquids, and the outer shell. Granted.... the gasses will permeate through, which is why you don't put stickers on any composite tank, but..... Ethanol does nothing to the poly ...... Tanks.

Well... In that case they don't know $h!^..... as there are no contact between the liquids, and the outer shell. Granted.... the gasses will permeate through, which is why you don't put stickers on any composite tank, but..... Ethanol does nothing to the poly ...... Tanks.

First off, I can't speak to the effects of ethanol on plastic tanks with any authority because I am not a chemist.

But from how certain you are that it has no ill effect, I'm betting you are, so thanks for the info smart guy.

Second, it does make sense conceptually that ethanol in the main tank could cause swelling that could cause cracks in the weak points of the outer shell.

I am from Missouri which adds ethanol to fuel (10% or higher) and I have had no issue with my tank... I am now in MD where ethanol isn't added where I purchase gas and I have no problem either.

Ethyl alcohol, or ethanol is a pretty gnarly solvent, but the noted trend with these tanks does not lend itself to ethanol as the culprit. Otherwise my BMW would be leaking every where and my tank is just fine as I pulled the whole thing off just the other day to make something.

My brand new '13 F700GS tank cracked on both sides within 2 weeks of purchase and after just 2 tanks of gas.... I'm pretty disappointed. More disappointed that I spent all this money on something that's been known bad for 2-3 years and with no signs of a permanent fix. So now, I have to live with the prospect that after my warranty period I'll have a cracked tank for the rest of it's life! I'm not too happy about it right now.... I'll keep my fingers crossed that something changes in the coming year.

But given how quickly my brand new bike developed issues, I sure do wonder!

I am not even sure it is dual wall. The liner is certainly different texture than the outside, but peering into the tank it may be nothing more than a liner of some type. Maybe when some ones fuel pump goes out they could check on that for me.

Worry about when it happens to you, because it did not happen to all. BMW did make a change in the curvature of the tank, supposedly to solve the problem. They held off on putting them out: IE design time.

The result was in our rush to get another tank some got old stock. Maybe they have some left over in the warehouse.

Nobody's tank leaked. The warranty on the bike is 3 years and if you wait to the end, you get 2 more years of parts warranty.

Wonder if any of the late model Husky tanks (beneath the seat) have ever cracked? Seems reasonable to assume they are made by same production facility.....look quite similar in material on the outside.

I am not even sure it is dual wall. The liner is certainly different texture than the outside, but peering into the tank it may be nothing more than a liner of some type. Maybe when some ones fuel pump goes out they could check on that for me.

I'm having a tank-ectomy done on Friday. If I don't get kicked out of the "kitchen" I'll try to peek over their shoulders and see what it looks like inside.